1. Field of the Invention
The Invention relates to a brake cylinder for the actuation of a vehicle brake, where a pressure chamber is furnished, wherein a movable membrane closes the pressure chamber, and wherein the pressure chamber can be subjected to a pressure agent for brake actuation, wherein a piston is furnished as a single piece mold part with a pressure plate and a piston shaft, where the piston is supported on the membrane and the piston can perform an actuating stroke with the membrane, where the piston shaft is furnished at its free end with a pressure piece, with a recess, which serves for the receiving of the actuating tappet for the actuation of the brake, wherein the brake cylinder includes a guide tube, where the piston shaft, the pressure piece and the actuating tappet are longitudinally movable disposed in the guide tube.
2. Brief Description of the Background of the Invention Including Prior Art
Such a brake cylinder is known from the printed European Patent Document EP-0 272 227 A2. A membrane as a movable wall performs a stroke in a pressure chamber of a brake cylinder based on its structure and its position upon subjection of the membrane to a force, where the stroke is transferred via a piston and an actuator tappet onto a device, which device is suitable to bring brake shoes to rest at a brake drum. A part formed as a pressure piece for receiving of the actuating tappet is disposed between the piston and the actuator tappet in the extension direction of the piston shaft. The pressure piece is furnished with a guide element formed as a piston cup with support elements and the pressure piece is guided longitudinally in a guide tube.
The conventional brake cylinder is employed for the actuation of wedge expanding brakes and is attached in connection with this property at a non-movable part of the wheel, i.e. at the brake drum. The attachment is performed in such a way that the guide tube is rigidly connected to the brake drum via a screw connection with its end disposed remote relative to the brake cylinder and such that the guide tube serves a free supporting connection element between the brake drum and the brake cylinder.
The advantageous property of the wedge expanding brake as compared to a conventional brake construction includes amongst others a reduction in the expanditure for the brake linkage and therewith associated a decrease of the elasticity of the linkage, where the elasticity of the linkage usually has to be compensated during braking as an undesired over throw. However, the brake cylinder, represents a mass in the recited attachment, which mass can introduce driving vibrations from the wheel or, respectively from the axle to the vehicle frame via the free supporting guide tube. The construction length of the guide tube represents a means for an overcoming of the distance between the brake cylinder and the brake drum, corresponding to the constructive realities or, respectively the available space in the region of the wheel and the brake drum, such that in case of wide tires or a lack of space based on a constructive embodiment of the spring suspension support on the axle, there can become necessary a longer guide tube with the disadvantage of an unfavorable displacement of the center of gravity. Therefore, a requirement exists for keeping the oscillating mass as low as possible, based on constructive elements and means, for purposes of reliability and extended life time of the brake device.